The present invention relates to a universal hand-free system for use with various types of cellular phones produced by different manufacturers. Such a hand-free system can automatically turn off a vehicle""s audio stereo system when incoming signals are being received by a cellular phone and automatically turn on the audio stereo system as the cellular phone terminates its operation, making communication quality of a cellular phone improved and driving safety increased. Moreover, by means of a signal cable, which can convert and discern incoming signals and signal criterion levels for various types of cellular phones produced by different manufacturers, the hand-free system of the present invention can be universally applied to a variety of cellular phones.
Deregulation of local communication business as well as the opening of domestic cellular phone markets results in multiple times increase in users of cellular phones. Under such a circumstance, consumers in the cellular phone markets require the functional advance of cellular phones more and more. Related peripheral equipment of cellular phones has been developed at a fast pace. In particular, hand-free systems for use with vehicles are the most prospective items. However, because new types of cellular phones are marketed at a fast pace, it is very common for members of a family to have a number of cellular phones of various types made by different makers. So, the hand-free system for use with one specific type of cellular phone is out of date now.
The inventor has noticed this kind of problem and has come up with a universal hand-free system for use with a plurality of types of cellular phones. For cellular phones produced by different makers or various types of cellular phones made by the same maker, the working voltages, the charging voltages, the volume of the output voice, and the pin holes of the output signal socket of the cellular phones are mostly different. Simple replacement of signal cables cannot solve the problem. Referring to FIG. 1, a prior art hand-free system 1 applicable to various types of cellular phones is provided with a signal cable 12. The cable has a plug connector 121 which is equipped with a plug embodiment 122 having a plurality of plug pins in conformance to the pin holes of a specific type of cellular phone. So, different types of cellular phones can be adapted to the prior art hand-free system of FIG. 1 by replacement of signal cable 12. Such an approach can be only applied to a particular type of cellular phone having a fixed configuration. It cannot be universally applied to all cellular phones.
Therefore, the primary object of the present invention is to provide a universal hand-free system in combination with a vehicle""s audio stereo system for use with various types of cellular phones. It mainly has an acoustic source control CPU, which can definitely discern various incoming signals of cellular phones of different brands and, incoming signals of a cellular phone can be automatically converted and output via speakers of a vehicle""s audio stereo system by means of associated circuits, making the use of cellular phones safer and easier.